Patent GB-1232475-A (GB)
IPC: B24B41/06
Filed: 1968-06-07
Abstract: 1,232,475. Grinding. LANDIS TOOL CO. 7 June, 1968 [7 June, 1967], No. 27202/68. Heading B3D. A work clamping unit for clamping a workpiece W against a rotating face plate 22 or like driving member comprises a spindle 60 mounted for rotation, a clamping member 74 mounted on the spindle in axial projecting relation, and flexing means 62, 72 incorporated in the spindle to compensate for misalignment and surface irregularities between the clamping member and a workpiece. The unit may be incorporated in a centreless grinding machine used for grinding the exterior peripheral surfaces of annular workpieces. The machine has a headstock 12 and tailstock 13 for holding a workpieee while it is ground by a grinding wheel 17, the workpieces being fed to and discharged from a space between the headstock and tailstock by a loader 15 having feed and discharge shoots 14, 16. The headstock has a faceplate 22 which is carried by a drive spindle 20 and has three radially disposed slots through which three work-engaging members of a centring device 25 carried by an axially-displaceable rod 26 can extend to engage and centre a workpiece W on the face-plate 22, the rod being movable against spring pressure by a fluid-operated motor. The tailstock consists of a plate 31 secured by bolts 32 to the machine and carrying a sleeve 34 receiving a tubular support 35 for limited sliding movement effected by a lever 53 rockable about a pivot 54 by a fluid-operated motor 47. One end of the support 35 carries a bearing 64 which receives one end 63 of the spindle 60 for rotation and axial movement. The end 63 is joined by flexible section 62 to the central portion 61 of the spindle. The central portion has a conical portion 71 for engaging a conical surface 38 on the support 35 and is connected by a flexible section 72 to the clamping member 74 having a face defined by angularly spaced portions. A sleeve 40 protects the spindle from dirt and moisture and air pressure supplied through an opening 59 is discharged between the sleeve 40 and clamping member 74. In operation, the centring device 25 and clamping member are initially retracted and a workpiece is supplied from the loader 15 on to a guide 29, the loader being operated by a fluid-operated motor, actuation of which is controlled automatically by an electrical relay circuit which also controls the clamping unit. The circuit operates a motor so that a spring advances the rod 26 and the centring device 25 engages and centres the workpiece W on the axis of the faceplate at the same time as motor 47 is operated at an initially low pressure to cause the support 35 and spindle 60 to advance and the clamping member 74 to press the workpiece at a relative low pressure against the face plate, the flexible section 72 accommodating irregularities of the surface of the workpiece. The spindle 60 is held central by the conical surfaces 38, 71 until the workpiece is clamped and then the support is advanced sufficiently to separate the surfaces 38, 71, the flexible section 62 permitting radial movement of the spindle to accommodate any out-of-line between the clamping member and face plate 22. Thereafter, high pressure is supplied to motor 47 to cause clamping member 74 to firmly hold the workpiece against the face plate while the workpiece is rough ground to a dimension determined by a gauge control. At this point the centring device 25 is retracted to remove radial forces acting on the workpiece prior to a spark-out grinding operation being effected to finish size whereupon the grinding wheel is retracted, the clamping member is retracted, and the loader operated to discharge the finished workpiece and feed a new workpiece to the guide 79.